Equilibrium exchange kinetics in n-alkyl-PEO polymeric micelles: single exponential relaxation and chain length dependence

In this communication we present first results on the chain exchange kinetics of n-alkyl-PEO polymeric micelles by time-resolved small angle neutron scattering. We found that the rate strongly depends on the alkyl-chain length and that the relaxation function almost perfectly follows the single exponential decay predicted by theory. The key achievement of this study is the experimental verification that core block polydispersity accounts for the almost logarithmic time decay in block copolymer micelles as recently suggested by Choi et al. The results thus directly show that unimer exchange is the main mechanism for molecular exchange in block copolymer micelles.